• Clean Technology
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• v.18 no.4
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• pp.426-431
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• 2012

Carbon-rich coal can be utilized as a fuel for direct carbon fuel cell (DCFC). However, left-behind ash after the electrochemical oxidation may hinder the electrochemical reactions. In this study, we produced ash-free coal (AFC) by thermal extraction and then tested it as a fuel for DCFC. DCFC was built based on solid oxide electrolyte and the electrochemical performance of AFC mixed with $K_2CO_3$ was compared with AFC only. Significantly enhanced power density was found by catalytic steam gasification of AFC. However, an increase of the power density by catalytic pyrolysis was negligible. This result indicated that a catalyst activated the steam gasification reactions, producing much more $H_2$ and thus increasing the power density, compared to AFC only. Results of a quantitative analysis showed much improved kinetics in AFC with $K_2CO_3$ in agreement with DCFC results. A secondary phase of potassium on yttria-stabilized zirconia (YSZ) surface was observed after the cell operation. This probably caused poor long-term behavior of AFC with $K_2CO_3$. A thin YSZ (30 ${\mu}m$ thick) was found to be higher in the power density than 0.9 mm of YSZ.

• Geotechnical Engineering
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• v.5 no.1
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• pp.7-18
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• 1989

In pile load tests on end bearing piles, generally, it is not possible to continue loading to the ultimate load. Thus, the concept of yield load has been introduced for determining design loads Iron the pile load test records. The conventional rules to determine the yield load were not available for evaluation on pile load test records obtained in 6 fields nearby westers 8r Southern Coasts in Korea. A new rule 9.as presented to determine easily the yield load, based on investigations on the pile load test records. The yield load of piles is determined at the infiection point on semi-logarithmic coordinates (P-logS), in which load is plotted in normal scale and settlement is plotted in logarithmic scale. This method may not only save much costs and times but also present safe luorking circumstances for pile load tests in field. It was found that the yield load represented the elastic limit of the pile load-settlement behalf.iota. The ultimate load, which is given at 25.4mm settlement on pile head, was 1.5 times of the yield load. The allowable long-term and short-term load capacities were, respectively, 50% and 75% of the yield load. The safety factors to get the allowable pile capacity were obtained as 2.0~4.0 for the equations to predict the static pile capacity.

• Journal of Gastric Cancer
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• v.9 no.1
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• pp.14-17
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• 2009

The clinical significance of hepatic resection for gastric metastases is controversial, even though hepatic resection has been widely accepted as a modality for colorectal metastases. Very few patients with gastric hepatic metastases are good candidates for hepatic resection because of multiple bilateral metastases, extrahepatic disease, or advanced cancer progression, such as peritoneal dissemination or extensive lymph node metastases. Therefore, several authors have reported the clinical significance of hepatic resection for gastric metastases in a small number of patients. Considering the present results with previous reports. The number and distribution of tumors in hepatic metastases from gastric cancer was considered based on the present and previous reports. Several authors have reported significantly better survival in patients with metachronous metastasis than in those with synchronous disease. However, metachronous hepatic resection necessitates the dissection of adhesions between the pancreas, liver, and residual stomach to prepare for Pringle's maneuver. Patients with unilobar liver metastasis, and/or metastatic tumors <4 cm in diameter may be good candidates for hepatic resection. Synchronous metastasis is not a contraindication for hepatic resection. Most of the long-term survivors underwent anatomic hepatic resection with a sufficient resection margin. After hepatic resection, the most frequent site of recurrence was the remaining liver, which was associated with a high frequency of mortality within 2 years. A reasonable strategy for improvement in survival would be to prevent recurrence by means of adjuvant chemotherapy and careful follow-up studies.

• Journal of Biomedical Engineering Research
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• v.20 no.1
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• pp.37-44
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• 1999

Because of bone resorption, wear of ultra-high molecular weight polyethylene(UHMWPE) in total knee arthroplasty has been recognized as a major factor in long-term failure of knee implant. The surface damage and the following harmful wear debris of UHMWPE is largely related to contact stress. Most of the previous studies focused on the contact condition only at the articulating surface of UHMWPE. Recently, contact stress at the metal-backing interface has been implicated as one of major factors in UHMWPE wear. Therefore, the purpose of the is study is to investigate the effect of the contact stress for different thickness, conformity friction coefficient, and flexion degree of the UHMWPE component in total knee system, considering the contact conditions at both interfaces. In this study, a two-dimensional non-linear plane strain finite element model was developed. The results showed that the maximum value of von-Mises stress occurred below the articulating surface and the contact stress was lower for the more conforming models. All-polyethylene component showed lower stress distribution than the metal-backed component. With increased friction coefficient on the tibiofemoral contact surface, the maximum shear stress increased about twofold.

• Economic and Environmental Geology
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• v.24 no.3
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• pp.319-327
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• 1991

Cheju is the biggest island in Korean peninsula, consisted entirely of volcanic rocks and pyroclastic sediments. The topography is characterized by wide basalt plain in the low altitude but at the center of island, basalt volcano rises 1,950m above sea-level. Surface drainage is very poor, therefore water supply has been dependent on ground water and natural springs. There are about 1,650 production wells and most of them yield $1,000{\sim}2,000mm^3/day$. According to increase of ground water use, saline water is intruded in the low altitude of coastal area. Specially in the eastern coastal area, the topography is extensively flat and the level of ground water is very close to sea-level, at which overuse of ground water has brought saline intrusion up to maximum 6km far from the coast. Hydrochemical monitoring on this salt water intrusion is now undertaken on long term base.

• Magazine of the Korean Society of Agricultural Engineers
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• v.8 no.1
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• pp.1011-1034
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• 1966

This thesis is the final report which has long been studied by the author to obtain the design basis for various hydrological constructions with the specific system suitable to the natural environmental conditions in Korea. This report is divided into two parts: one is to estimate runoff volume from watersheds and the other to estimate the peak discharge for a single storm. According to the result of observed runoff record from watersheds, it is known that Kajiyama formula is useful instrument in estimating runoff volume from watersheds in this country. But it has been found that this formula shows us 20-30% less than the actual flow. Therefore, when wihed to bring a better result, the watershed characteristics coefficient in this formula, that is, f-value, should be corrected to 0.5-0.8. As for the method to estimate peak discharge from drainage basin, the author proposes to classify it in two ways; one is small size watershed and the other large size watershed. The maximum -flood discharge rate $Q_p$ and time to peak Pt obtained from the observed record on the small size watershed are compared by various methods and formulas which are based upon the modern hydrological knowledge. But it was fou.d that it. was not a satisfied result. Therefore, the author proposes. tocomputate $Q_p$, to present 4.0-5.0% for the total runoff volume ${\Sigma}Q$.${\Sigma}Q$ is computed under the assumption of 30mm 103s in watershed per day and to change the theoritical total flow volume to one hour dura tion total flow rate when design daily storm is given. Time to peak Pt is derived from three parameters which are u,w,k. These are computed by relationship between total runoff volume (ha-m unit)and $Q_p$. (C.M.S. unit). Finally, the author checked out these results obtained from 51 hydrographs and got a satisfied result. Therefore the author suggested the model of design dimensionless unit-hydrograph. And the author believes that this model will be much available at none runoff record river site. In the large size watersheds in Korea when the maximum discharge occurs, the effective rainfall is two consequtive stormy days. So the loss in watershed was assutned as 6Omm/2days,and the author proposed 3-hour-daration hydrograph flow distribution percentage. This distribution percentage will be sure to form the hydrograph coordinate.

• Magazine of the Korean Society of Agricultural Engineers
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• v.11 no.2
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• pp.1644-1650
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• 1969

In the design of general hydrological structures, it is well know that the design flood is of importance in the design of those structures. As the design flood is estimated using the design storm, the design storm is defined by the rainfall intensity itself. Though I had studied and reported many times the reports about the rainfall-intensity in my country, poorly I did not study the long-period variation of the intensity through each section in my country before. But now, in the basin area of the Han river and the Keum river, the self-recorded rainfall charts of the single storms, which are mostly above rainfall amount of 30mm and data of about 4500 with the 150 stationyear, were analyzed, And then, the intensity formula of the hourly unit is estimated using the period from 10 minutes to 5 days. The method to analyze and estimate them, and the final results will be summarized as mentioned below: (i) At first I intended to select out the homogeneous watersheds of three, one in the Han river and two in the Keum river. But I would select the northern and the sourthern river basins, and westward from Koan station, in the basins of the Han river. Also I would select the upstream area, and the downstream area including the watershed of Chungioo, Kongjoo, Chupungryung, and the Mt. Sock, in the basins of the Keum river. Finally, I could find that there couldn't in the Keum river basin. So, I decided out and analyze only river basins of the Han river with limitation mentioned above. (ii) The statistical method to select out the homogenous watersheds is the test of homogeneous variance, and it is estimated from the following equation: $$X_{k1}^2=[{\Sigma}(n_i-1)log\bar{S^2}-\Sigma(n_i-1)log\bar{S^2}]{\times}loge$$ (iii) Actually, each homogeneous watershed has individually its own intensity formula, But I would express them as the actual amount, because the equation of intensity variance is experiential and theoretical equation of the variance. Therefore the caluating equation is actually more convenient in the actual uses. (iv) This report is one of the series for me to give the basis to the actual designs. The cost for this study is provided by the Ministry of Construction. And the designs of the hydrological structures in the watersheds with limitation mentioned above may be concerned with and based upon this report.

• Archives of Plastic Surgery
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• v.37 no.4
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• pp.391-395
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• 2010

Purpose: Given that the critical nature of the microvascular anastomosis to what is often a long and difficult reconstructive operation, trainees need to have a high level of microsurgical competence before being allowed to perform microsurgery on patients. Some artificial substitutes and dead or live animal models have been used to improve manual dexterity under the operating microscope. Yet, most surgeons are not equipped with such models, so search for easy available and appropriate microsurgical practice model have been an issue. Umbilical artery, placental vessels and gastroepiploic arteries have been previously suggested as a microsurgical training model, which involves other surgical departments. The purpose of this article is to introduce that saphenous vein specimen obtained from varicose vein surgery is useful and has many advantages as training model for the practice of microvascular anastomosis. Methods: The conventional technique using perforation/inversion method with a metallic stripper is widely performed for varicose vein patients. The stripper is inserted through disconnected safeno-femoral junction and retrieved at the knee or the medial side of ankle. The length of saphenous vein specimens removed is about that of one's leg and inversed from inside out. Obtained saphenous vein specimens are re-inversed and cleansed with normal saline, to be readily available for microsurgical practice. Preserved in a squeezed wet saline gauze and refrigerated, frozen or glycerated specimens were investigated into their comparative quality for microsurgical practice. Results: Varicose vein surgery remains one of the common operations performed in the field of plastic surgery. Convenient informed consent regarding the vessel donation can be easily signed. The diameter of the obtained saphenous vein is as variable as 1.5 to 6 mm, which is already stripped, and is in sufficient length corresponding to that of patient's leg. Vessels specimens were available for microsurgical practice within 1 week period when preserved with squeezed wet saline gauze, and the preservation period could be extended monthly by freezing it. Conclusion: Saphenous vein obtained from varicose vein patients provide with variable size of vessel lumen with sufficient length. The practice can be cost effective and does not require microsurgical laboratory. Additionally there is no need of involving other surgical departments in acquiring vessel specimens. Furthermore, simple preservation method of refrigerating for a week or freezing with squeezed wet saline gauze for a month period, allow the saphenous vein obtained after varicose vein surgery as an excellent model for the microsurgical practice.

• Journal of Chest Surgery
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• v.18 no.4
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• pp.679-691
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• 1985

Ninety patients underwent mitral valvular heart surgery associated with or without aortic valve surgery and subjected to a clinical study in relation to their control of postoperative atrial fibrillation. There were 26 males and 64 females ranged in age from 16 to 56 years with a mean of 35.2 years. Systemic arterial embolizations were observed in 11 patients [12.2%]. Four patients of them were in normal sinus rhythm and 7 in atrial fibrillation. Out of these, left atrial thrombi were found only in 2 at the operation. Intraoperatively confirmed left atrial thrombi were in 16 patients [17.7%] of all 90 patients: Eleven patients occurred at the age of more than 40 years, 14 were in atrial fibrillation and 2 only had previous episodes of systemic arterial embolization. Sixty three patients underwent isolated mitral valve surgery [OMC 28, MVR 35] and 27 patients associated with aortic valve surgery along with mitral valve [OMC+AVR 13, MVR+AVR 14]. Preoperatively, 44 patients [48.9%] were in normal sinus rhythm. Of them, 35 patients [79.5%] revealed normal sinus rhythm thoroughly after operation without any aid of digitalis or quinidine and 5 patients [11.4%] restored normal sinus rhythm with digitalization alone. Other 3 patients converted to normal sinus rhythm with the addition of quinidine, however, in 1 patient who was resistant to quinidine therapy, electrocardioversion was carried out on the postoperative third week showing normal sinus rhythm. Thus, the most atrial fibrillations that occurred for the first time in the postoperative period, were able to reverted to normal sinus rhythm responding well to antiarrhythmic therapy. Preoperatively, 46 patients [51.1%] were in atrial fibrillation. Of them, only 5 patients returned to sinus rhythm after operation without any aid of digitalis or quinidine and other 5 restored normal sinus rhythm with digitalization: namely 2 restored within early postoperative period and 3 after more than 3 months. Eight patients well responded to quinidine therapy showing normal Sinus rhythm. So far, 25 patients have remained in persistent atrial fibrillation on 6 to 36 months follow-up. In view of these, 17 patients [68%] were over 40 years of age, 22[80%] had long duration of symptom over 5 years and 10[40%] have had atrial thrombi before operation. Left atrial dimension were still more than 40mm in 21 patients on follow up M-mode echocardiogram. One month after operation, 87 hospital survivors were improved by at least one functional NYHA class. There were 3 operative deaths [3.3%, bleeding 1, LCOS 2] and 4 late deaths [LCOS 1, valve thrombosis 1, late bleeding 1, fulminant hepatitis 1] during follow-up period. According to our limited experience, we may conclude that better results will be expected with the addition of quinidine therapy judiciously in the cases of postoperative persistent atrial fibrillation who were aged or had longer history of symptom and left atrial thrombi.

• Journal of Chest Surgery
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• v.32 no.3
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• pp.262-269
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• 1999

Background: To review the middle and long term results of aortic valve replacement(AVR) for 11 years, we surveyed and followed up the patients who underwent AVR. Material and Method: Between Feb. 1986 and May 1997, 134 patients underwent AVR. The patients consisted of 71 men and 63 women whose mean age was 38.9 years, ranging from 17 to 70. Result: The concomitant operations were 62 mitral valve replacement(MVR), 14 MVR + tricuspid valve annuloplasty, 10 Cabrol operation, 16 aortic annulus widening, and so forth. We used 119 mechanical(75 St. Jude Medical, 38 CarboMedics, 6 Sorin) and 15 tissue (Carpentier-Edwards) valves. Early postoperative complications occurred in 35 cases; 9 congestive heart failure, 6 low cardiac output, 5 postoperative bleeding, 5 pleural effusion, and so forth. There were 13 early postoperative deaths(9.7%) due to low cardiac output(5), CHF (2), disseminated intravascular coagulopathy(2), and so forth. The cumulative total follow-up period was 452.7 patient-years with a mean of 3.4${\pm}$3.1 years/patient. There were 9 cases of valve-related complications; anticoagulant-related bleeding(4), prosthetic valve endocarditis(2), thromboembolism(2) and prosthetic valve failure(1) occured at rate of 0.9, 0.4, 0.4, 0.2%/ pt-yr, respectively. Late valve-related death occurred in 3 cases(2.0%/pt-yr) associated with anticoagulant-related bleeding(2) and prosthetic valve endocarditis(1). Conclusion: Actuarial survival rate by Kaplan-Meier method was 91.0${\pm}$4.3 % at 11 years.